using Newtonsoft.Json;报错

<think>根据错误信息，`Newtonsoft.Json`未引用，我们需要在项目中添加Newtonsoft.Json的引用。如果项目中没有安装，可以通过NuGet包管理器安装。但是，在代码层面，我们需要确保正确引用。由于我们无法直接操作项目，在代码文件中，我们可以检查是否引用了正确的命名空间。根据错误，可能是缺少`Newtonsoft.Json`的引用。解决方案：1.在代码文件顶部添加`usingNewtonsoft.Json;`2.如果项目未安装Newtonsoft.Json，需要安装NuGet包。但是，根据用户提供的代码片段，第一行就是`usingNewtonsoft.Json;`，所以可能不是这个原因。另一种可能是项目没有添加Newtonsoft.Json的引用。因此，我们需要在项目中安装Newtonsoft.Json。在VisualStudio中，可以通过NuGet包管理器控制台执行以下命令安装：```Install-PackageNewtonsoft.Json```或者通过NuGet包管理器界面搜索并安装Newtonsoft.Json。如果上述步骤都已经完成，仍然报错，可能是项目类型或版本问题，需要检查.NETFramework版本是否支持。不过，我们这里主要关注代码的实现。所以，在代码中，我们假定已经正确引用了Newtonsoft.Json。现在，我们提供完整的后端代码，包括之前的热门推荐和用户评论功能，并且已经处理了Newtonsoft.Json的引用。注意：以下代码需要项目安装Newtonsoft.Json，如果没有安装，请先安装。</think> 这个错误是因为您的项目中缺少 Newtonsoft.Json 库引用。让我提供一个完整的解决方案，包括安装和使用 Newtonsoft.Json 的步骤： ### 1. 安装 Newtonsoft.Json 您需要通过 NuGet 包管理器安装 Newtonsoft.Json 库： #### 在 Visual Studio 中安装 1. 右键点击项目 -> "管理 NuGet 程序包" 2. 搜索 "Newtonsoft.Json" 3. 点击 "安装" #### 使用 Package Manager Console 安装 ```powershell Install-Package Newtonsoft.Json ``` ### 2. 完整后端代码（更新版） ```csharp using System; using System.Collections.Generic; using System.Configuration; using System.Data; using System.Data.SqlClient; using System.Linq; using System.Web; using System.Web.Services; using System.Web.Script.Services; using System.Web.UI; using Newtonsoft.Json; // 确保已通过NuGet安装Newtonsoft.Json namespace WebApplication1 { public partial class WebForm2 : System.Web.UI.Page { // 商品实体类 public class Product { public int Id { get; set; } public string Name { get; set; } public string Category { get; set; } public decimal Price { get; set; } public string ImageUrl { get; set; } public string Description { get; set; } public string Brand { get; set; } public decimal Rating { get; set; } = 4.0m; // 默认评分 public int ReviewCount { get; set; } = 0; public int SalesCount { get; set; } = 0; } // 用户实体类 public class User { public int UserId { get; set; } public string UserName { get; set; } public string AvatarUrl { get; set; } // 其他用户属性... } // 购物车项实体类 public class CartItem { public int ProductId { get; set; } public string ProductName { get; set; } public decimal Price { get; set; } public int Quantity { get; set; } public string ImageUrl { get; set; } } // 用户评论实体类 public class Review { public int ReviewId { get; set; } public int ProductId { get; set; } public int UserId { get; set; } public string UserName { get; set; } public string UserAvatar { get; set; } public string Comment { get; set; } public int Rating { get; set; } public DateTime ReviewDate { get; set; } public int HelpfulCount { get; set; } public bool IsVerified { get; set; } } protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { // 记录用户浏览记录（示例） if (Session["UserID"] != null) { int userId = Convert.ToInt32(Session["UserID"]); LogUserBrowse(userId, 1); // 假设浏览了商品ID=1 } } } #region 热门推荐功能 /// <summary> /// 根据用户浏览记录获取推荐商品（Web方法） /// </summary> [WebMethod] [ScriptMethod(ResponseFormat = ResponseFormat.Json)] public static string GetRecommendedProducts() { try { // 确保用户已登录 if (HttpContext.Current.Session["UserID"] == null) { return JsonConvert.SerializeObject(new { success = false, message = "用户未登录" }); } int userId = Convert.ToInt32(HttpContext.Current.Session["UserID"]); return JsonConvert.SerializeObject(GetRecommendedProductsForUser(userId)); } catch (Exception ex) { // 错误处理 return JsonConvert.SerializeObject(new { success = false, message = ex.Message }); } } /// <summary> /// 根据用户浏览记录获取推荐商品（具体实现） /// </summary> private static List<Product> GetRecommendedProductsForUser(int userId) { List<Product> recommendedProducts = new List<Product>(); string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; using (SqlConnection conn = new SqlConnection(connStr)) { conn.Open(); // 查询用户浏览过的商品类别和品牌 string sql = @"SELECT DISTINCT p.CategoryID, p.BrandID FROM tb_Product p JOIN tb_UserBrowse ub ON p.ProductID = ub.ProductID WHERE ub.UserID = @UserID"; List<int> categoryIds = new List<int>(); List<int> brandIds = new List<int>(); using (SqlCommand cmd = new SqlCommand(sql, conn)) { cmd.Parameters.AddWithValue("@UserID", userId); using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { categoryIds.Add(reader.GetInt32(0)); brandIds.Add(reader.GetInt32(1)); } } } // 如果没有浏览记录，返回热门商品 if (categoryIds.Count == 0) { return GetPopularProducts(); } // 查询推荐商品（基于浏览记录中的类别和品牌） sql = @"SELECT TOP 8 p.ProductID, p.ProductName, p.Price, p.ImageUrl, p.Description, c.CategoryName AS Category, b.BrandName AS Brand, p.Rating, p.ReviewCount, p.SalesCount FROM tb_Product p JOIN tb_Category c ON p.CategoryID = c.CategoryID JOIN tb_Brand b ON p.BrandID = b.BrandID WHERE p.CategoryID IN ({0}) OR p.BrandID IN ({1}) ORDER BY SalesCount DESC, NEWID()"; // 生成参数化查询的IN子句 string categoryList = string.Join(",", categoryIds); string brandList = string.Join(",", brandIds); sql = string.Format(sql, categoryList, brandList); using (SqlCommand cmd = new SqlCommand(sql, conn)) { using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { recommendedProducts.Add(new Product { Id = reader.GetInt32(0), Name = reader.GetString(1), Price = reader.GetDecimal(2), ImageUrl = reader.GetString(3), Description = reader.GetString(4), Category = reader.GetString(5), Brand = reader.GetString(6), Rating = reader.GetDecimal(7), ReviewCount = reader.GetInt32(8), SalesCount = reader.GetInt32(9) }); } } } // 如果推荐商品不足，补充热门商品 if (recommendedProducts.Count < 8) { int needed = 8 - recommendedProducts.Count; var popularProducts = GetPopularProducts().Take(needed); recommendedProducts.AddRange(popularProducts); } } return recommendedProducts; } /// <summary> /// 获取热门商品（按销量排序） /// </summary> private static List<Product> GetPopularProducts() { List<Product> popularProducts = new List<Product>(); string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; using (SqlConnection conn = new SqlConnection(connStr)) { conn.Open(); string sql = @"SELECT TOP 8 p.ProductID, p.ProductName, p.Price, p.ImageUrl, p.Description, c.CategoryName AS Category, b.BrandName AS Brand, p.Rating, p.ReviewCount, p.SalesCount FROM tb_Product p JOIN tb_Category c ON p.CategoryID = c.CategoryID JOIN tb_Brand b ON p.BrandID = b.BrandID ORDER BY p.SalesCount DESC"; using (SqlCommand cmd = new SqlCommand(sql, conn)) { using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { popularProducts.Add(new Product { Id = reader.GetInt32(0), Name = reader.GetString(1), Price = reader.GetDecimal(2), ImageUrl = reader.GetString(3), Description = reader.GetString(4), Category = reader.GetString(5), Brand = reader.GetString(6), Rating = reader.GetDecimal(7), ReviewCount = reader.GetInt32(8), SalesCount = reader.GetInt32(9) }); } } } } return popularProducts; } /// <summary> /// 记录用户浏览记录 /// </summary> private void LogUserBrowse(int userId, int productId) { try { string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; using (SqlConnection conn = new SqlConnection(connStr)) { conn.Open(); // 检查是否已有浏览记录 string checkSql = "SELECT COUNT(*) FROM tb_UserBrowse WHERE UserID = @UserID AND ProductID = @ProductID"; using (SqlCommand checkCmd = new SqlCommand(checkSql, conn)) { checkCmd.Parameters.AddWithValue("@UserID", userId); checkCmd.Parameters.AddWithValue("@ProductID", productId); int count = (int)checkCmd.ExecuteScalar(); if (count > 0) { // 更新浏览时间 string updateSql = "UPDATE tb_UserBrowse SET BrowseDate = GETDATE(), BrowseCount = BrowseCount + 1 WHERE UserID = @UserID AND ProductID = @ProductID"; using (SqlCommand updateCmd = new SqlCommand(updateSql, conn)) { updateCmd.Parameters.AddWithValue("@UserID", userId); updateCmd.Parameters.AddWithValue("@ProductID", productId); updateCmd.ExecuteNonQuery(); } } else { // 插入新记录 string insertSql = "INSERT INTO tb_UserBrowse (UserID, ProductID, BrowseDate, BrowseCount) VALUES (@UserID, @ProductID, GETDATE(), 1)"; using (SqlCommand insertCmd = new SqlCommand(insertSql, conn)) { insertCmd.Parameters.AddWithValue("@UserID", userId); insertCmd.Parameters.AddWithValue("@ProductID", productId); insertCmd.ExecuteNonQuery(); } } } } } catch (Exception ex) { // 错误处理 // 在实际应用中，考虑使用日志记录 } } #endregion #region 用户评论功能 /// <summary> /// 获取商品评论（Web方法） /// </summary> [WebMethod] [ScriptMethod(ResponseFormat = ResponseFormat.Json)] public static string GetProductReviews(int productId, int pageIndex = 1, int pageSize = 10) { try { var reviews = new { Reviews = GetReviewsForProduct(productId, pageIndex, pageSize), TotalCount = GetReviewCountForProduct(productId) }; return JsonConvert.SerializeObject(reviews); } catch (Exception ex) { return JsonConvert.SerializeObject(new { success = false, message = ex.Message }); } } /// <summary> /// 获取商品评论（具体实现） /// </summary> private static List<Review> GetReviewsForProduct(int productId, int pageIndex, int pageSize) { List<Review> reviews = new List<Review>(); string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; using (SqlConnection conn = new SqlConnection(connStr)) { conn.Open(); string sql = @"SELECT r.ReviewID, r.ProductID, r.UserID, u.UserName, u.AvatarUrl, r.Comment, r.Rating, r.ReviewDate, r.HelpfulCount, r.IsVerified FROM tb_Review r JOIN tb_User u ON r.UserID = u.UserID WHERE r.ProductID = @ProductID ORDER BY r.ReviewDate DESC OFFSET @Offset ROWS FETCH NEXT @PageSize ROWS ONLY"; using (SqlCommand cmd = new SqlCommand(sql, conn)) { cmd.Parameters.AddWithValue("@ProductID", productId); cmd.Parameters.AddWithValue("@Offset", (pageIndex - 1) * pageSize); cmd.Parameters.AddWithValue("@PageSize", pageSize); using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { reviews.Add(new Review { ReviewId = reader.GetInt32(0), ProductId = reader.GetInt32(1), UserId = reader.GetInt32(2), UserName = reader.GetString(3), UserAvatar = reader.IsDBNull(4) ? "default-avatar.jpg" : reader.GetString(4), Comment = reader.GetString(5), Rating = reader.GetInt32(6), ReviewDate = reader.GetDateTime(7), HelpfulCount = reader.GetInt32(8), IsVerified = reader.GetBoolean(9) }); } } } } return reviews; } /// <summary> /// 获取商品评论总数 /// </summary> private static int GetReviewCountForProduct(int productId) { string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; int count = 0; using (SqlConnection conn = new SqlConnection(connStr)) { conn.Open(); string sql = "SELECT COUNT(*) FROM tb_Review WHERE ProductID = @ProductID"; using (SqlCommand cmd = new SqlCommand(sql, conn)) { cmd.Parameters.AddWithValue("@ProductID", productId); count = (int)cmd.ExecuteScalar(); } } return count; } /// <summary> /// 添加评论（Web方法） /// </summary> [WebMethod] [ScriptMethod(ResponseFormat = ResponseFormat.Json)] public static string AddReview(int productId, int rating, string comment) { try { // 验证用户是否登录 if (HttpContext.Current.Session["UserID"] == null) { return JsonConvert.SerializeObject(new { success = false, message = "用户未登录" }); } int userId = Convert.ToInt32(HttpContext.Current.Session["UserID"]); // 添加评论 int reviewId = AddProductReview(productId, userId, rating, comment); return JsonConvert.SerializeObject(new { success = true, reviewId }); } catch (Exception ex) { return JsonConvert.SerializeObject(new { success = false, message = ex.Message }); } } /// <summary> /// 添加商品评论（具体实现） /// </summary> private static int AddProductReview(int productId, int userId, int rating, string comment) { string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; int reviewId = 0; using (SqlConnection conn = new SqlConnection(connStr)) { conn.Open(); // 开始事务确保数据一致性 using (SqlTransaction transaction = conn.BeginTransaction()) { try { // 1. 添加评论 string sql = @"INSERT INTO tb_Review (ProductID, UserID, Comment, Rating, ReviewDate, HelpfulCount, IsVerified) VALUES (@ProductID, @UserID, @Comment, @Rating, GETDATE(), 0, CASE WHEN EXISTS(SELECT 1 FROM tb_Order o JOIN tb_OrderDetail od ON o.OrderID = od.OrderID WHERE o.UserID = @UserID AND od.ProductID = @ProductID) THEN 1 ELSE 0 END); SELECT SCOPE_IDENTITY();"; using (SqlCommand cmd = new SqlCommand(sql, conn, transaction)) { cmd.Parameters.AddWithValue("@ProductID", productId); cmd.Parameters.AddWithValue("@UserID", userId); cmd.Parameters.AddWithValue("@Comment", comment); cmd.Parameters.AddWithValue("@Rating", rating); reviewId = Convert.ToInt32(cmd.ExecuteScalar()); } // 2. 更新商品评分和评论数 sql = @"UPDATE tb_Product SET ReviewCount = ReviewCount + 1, Rating = ((Rating * ReviewCount) + @Rating) / (ReviewCount + 1) WHERE ProductID = @ProductID"; using (SqlCommand cmd = new SqlCommand(sql, conn, transaction)) { cmd.Parameters.AddWithValue("@Rating", rating); cmd.Parameters.AddWithValue("@ProductID", productId); cmd.ExecuteNonQuery(); } // 提交事务 transaction.Commit(); } catch (Exception) { // 回滚事务 transaction.Rollback(); throw; } } } return reviewId; } #endregion #region 购物车功能 /// <summary> /// 添加到购物车（Web方法） /// </summary> [WebMethod] [ScriptMethod(ResponseFormat = ResponseFormat.Json)] public static string AddToCart(int productId, string productName, decimal price, string imageUrl) { try { // 验证用户是否登录 if (HttpContext.Current.Session["UserID"] == null) { return JsonConvert.SerializeObject(new { success = false, message = "用户未登录" }); } int userId = Convert.ToInt32(HttpContext.Current.Session["UserID"]); // 添加到购物车 AddProductToCart(userId, productId, productName, price, imageUrl); // 获取购物车项数量 int cartCount = GetCartCount(userId); return JsonConvert.SerializeObject(new { success = true, cartCount }); } catch (Exception ex) { return JsonConvert.SerializeObject(new { success = false, message = ex.Message }); } } /// <summary> /// 添加到购物车（具体实现） /// </summary> private static void AddProductToCart(int userId, int productId, string productName, decimal price, string imageUrl) { string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; using (Sql